1. Field of the Invention
This invention relates to a method for determining the quality of a protective coating located on a structure. More specifically, this invention provides a method for on-line monitoring of the quality of aluminum anodization on the inside of a reactor chamber wherein semiconductor substrates are processed in a plasma of a processing gas.
2. Description of the Prior Art
Aluminum hard anodization has been widely used in the semiconductor industry for years due to its unique properties, such as high corrosion resistance and surface micro-hardness, low cost, low contamination levels, manufacturing capability, and ease of application. Anodization is a major coating applied to a structure within a plasma reactor chamber, such as reactor walls, gas distribution plates (GDPs), chamber lids, and pedestals for electrostatic chuck application. In recent years, a tremendous amount of work has been done to find new materials or new surface coatings to replace aluminum hard anodization. Although there has been great progress in identifying new materials and new coatings, the complete replacement of aluminum anodize with new chamber materials or coatings is presently not foreseeable in the near future.
Aluminum anodize quality depends on many factors, such as the texture of the raw aluminum alloys, the type of aluminum alloy used, masking, cleaning, and post treatment processes. Therefore, the use of very detailed procedures for aluminum anodizing process, for control of the content and level of impurities in the anodize line, and for statistical process control (SPC) are critical. In a plasma reactor the difference between a good and bad aluminum anodize can have a 10 to 20 times difference in lifetime of the aluminum anodize. Aluminum anodize failure can occur in all types of reactor structures, such as reactor lids and in the pumping-port area. The failure of aluminum anodization may not only cause gas (e.g., Cl2) flow verification issues, but may also provide Al2O3 particles which can damage the production wafer. Traditional anodization analytical techniques, such as dielectric voltage breakdown, have played an important role in the past to provide critical information for the correct assessment of aluminum anodize quality, but none of these analytical techniques have the capabilities of providing more relevant critical information on aluminum anodize, such as corrosion resistance. Also, none of the traditional analytical techniques have the capability of in-situ monitoring the quality of aluminum anodize.
Therefore, what is needed and what has been invented is a method for determining the quality of a protective coating (e.g., aluminum hard anodization) located on the inside of a reactor chamber where semiconductor substrates are processed (e.g., by etching, vapor deposition, etc.) in a plasma of a processing gas. What is further needed and what has been invented is a method for on line monitoring of the quality of a coating or layer supported by a structure on the inside of a reactor chamber.
The present invention broadly provides a method for determining the quality of a protective coating on the inside of a reactor chamber wherein substrates are processed comprising the steps of:
a) generating a basis (e.g. a standard scatter band of impedance) as an acceptable standard for the quality (e.g. protective characteristics such as resistance to corrosion/erosion, etc).
b) processing (e.g. etching, depositing a layer on, etc) at least one substrate in a reactor chamber containing a protective coating for protecting the inside of the reactor chamber during processing of the at least one substrate; and
c) determining the quality of the protective coating after the processing of step (b).
In the foregoing method for determining the quality of a protective coating, the determining of step (c) comprises measuring protective characteristics of the protective coating and comparing the measured protective characteristics with the generated basis of step (a) which preferably contains standard protective characteristics that are acceptable in quality for processing substrates. The measuring of the protective characteristics of the protective coating comprises contacting the protective coating with a first electrode, and coupling a second electrode to a chamber structure supporting the protective coating.
The present invention also broadly provides a method for determining the quality of a layer on a structure in a reactor chamber after processing substrates therein. The method comprises the steps of:
a) providing a reactor chamber containing a chamber structure (e.g. a reactor chamber wall, a gas distribution plate, a rector chamber lid, a pedestal, etc.) supporting a chamber layer (e.g., anodized aluminum) having characteristics acceptable for processing substrates;
b) generating a standard scatter band of impedance from a set of coupons wherein each of the coupons supports a respective coupon layer having characteristics acceptable for use on the chamber structure in the reactor chamber of step (a);
c) disposing a substrate in the reactor chamber of step (a);
d) introducing a processing gas into the reactor chamber of step (a);
e) introducing processing power into the reactor chamber of step (a) for processing (e.g., etching or depositing) a layer on the substrate in a plasma of the processing gas, causing the chamber layer of the chamber structure to develop post-processing characteristics;
f) determining an impedance spectra of the chamber layer of step (e); and
g) determining if the impedance spectra of step (f) for the chamber layer of step (e) falls within the standard scatter band of impedance of step (b), indicating that the chamber layer of step (e) with the post-processing characteristics is acceptable in quality for processing of substrates.
In the foregoing method for determining the quality of a layer on a structure, the determining of step (f) comprises contacting the chamber layer with an electrode and coupling the chamber structure to another electrode. The chamber structure may be any suitable structure such as a chamber wall, a gas distribution plate, a chamber lid, a pedestal, or any of the like. The standard scatter band of impedance has a lower limit, and the determining step (g) comprises determining if the impedance spectra is located above the lower limit, indicating that the step (e) chamber layer possesses an acceptable quality for continuing the processing of substrates.
The present invention further also accomplishes its desired objects by broadly providing a method for on-line monitoring of the quality of a coating on the inside of a reactor chamber for processing substrates comprising the steps of:
a) generating a standard scatter band of impedance from a set of coupons wherein each of said coupons supports a respective coupon layer having characteristics acceptable for providing a protective layer on a structure in a reactor chamber wherein substrates are processed;
b) disposing a substrate in a reactor chamber containing a chamber structure supporting a protective coating to protect the chamber structure from processing conditions resulting from processing of the substrate within the reactor chamber;
c) processing the substrate of step (b) within the reactor chamber, causing the protective coating on the chamber structure to be affected;
d) determining an impedance spectra for the affected protective coating of step (c);
e) comparing the impedance spectra of step (d) with the standard scatter band of impedance of step (a) and determining that the affected protective coating is acceptable in quality for continuing the processing of substrates;
f) processing at least one additional substrate within the reactor chamber, causing the protective coating on the chamber structure to be further affected;
g) determining an impedance spectra for the further affected protective coating; and
h) comparing the impedance spectra of step (g) with the standard scatter band of impedance of step (a) for on-line monitoring of the quality of the protective coating on the chamber structure and to determine if the further affected protective coating is acceptable in quality for continuing the processing of substrates.
The present invention also broadly provides a chamber assembly for processing substrates in a plasma of a processing gas. The chamber assembly includes a processing chamber having a chamber coating, and a processing zone wherein substrates are processed. A pedestal assembly is disposed in the processing zone and has a receiving surface for receiving a substrate. A first electrode contacts the chamber coating and a second electrode is coupled to the processing chamber. The chamber assembly further includes a processing power source; a processing gas-introducing assembly, engaged to the processing chamber, for introducing a processing gas into the processing chamber; and a processing power-transmitting member connected to the processing power source for transmitting power into the processing zone to aid in sustaining a plasma from a processing gas within the processing zone of the processing chamber. The processing chamber comprises a chamber wall supporting a dielectric window. The chamber coating may be supported by the chamber wall and the second electrode may be respectively coupled to the chamber wall. Preferably, the first electrode and the second electrode is coupled to an EIS measurement and data acquisition system.